May 2017 - ghc-tickets

[GHC] #11834: GHC master, not compiling on Archlinux
by GHC 29 May '17

29 May '17

#11834: GHC master, not compiling on Archlinux -------------------------------------+------------------------------------- Reporter: nitrix | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: (Linking) | Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Building GHC (amd64) | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- /usr/bin/ld: -r and -pie may not be used together http://lpaste.net/159726 It appears on Archlinux, with GCC version 5.3.0, there's an implicit -pie flag passed to `ld`. I looked into compiler/main/DriverPipeline.hs at joinObjectFiles, it is unconditionally doing "-Wl,-r", thus the error above. One suggested fix on IRC is to modify getCompilerInfo to know if it supports -no-pie, then add it to the flags that are used. I tried and got somewhere lost in compiler/main/DynFlags.hs. (Completely new to GHC) Hopefully someone can figure it out, it seems important for development and I really want to get involved :) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11834> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13306: Problems with type inference for static expressions
by GHC 29 May '17

29 May '17

#13306: Problems with type inference for static expressions -------------------------------------+------------------------------------- Reporter: edsko | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I've been running into some difficulties with type inference for static expressions; I suspect not enough type information might be propagated down. Below are a number of tests, all of which compare type inference for `static` with type inference for a function {{{#!hs fakeStatic :: Typeable a => a -> StaticPtr a fakeStatic = undefined }}} Apart from syntactic checks, I'd expect `static <expr>` and `fake`Static <expr>` to behave more or less the same, but they don't. Here are some examples: {{{#!hs {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE StaticPointers #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE GADTs #-} module Main where import Data.Proxy import Data.Typeable import GHC.StaticPtr {------------------------------------------------------------------------------- Setup -------------------------------------------------------------------------------} -- Some kind of non-injective type family type family NonInj a where NonInj Bool = () NonInj Char = () -- To compare against the real static fakeStatic :: Typeable a => a -> StaticPtr a fakeStatic = undefined {------------------------------------------------------------------------------- Test 1: identity function -------------------------------------------------------------------------------} f1 :: Proxy a -> NonInj a -> NonInj a f1 Proxy = id f2 :: forall a. Typeable (NonInj a) => Proxy a -> StaticPtr (NonInj a -> NonInj a) f2 Proxy = fakeStatic id -- Fails with: -- -- Couldn't match type ‘a0’ with ‘NonInj a’ -- Expected type: NonInj a -> NonInj a -- Actual type: a0 -> a0 -- The type variable ‘a0’ is ambiguous -- f3 :: forall a. Typeable (NonInj a) => Proxy a -> StaticPtr (NonInj a -> NonInj a) -- f3 Proxy = static id -- Fails with the same error -- f4 :: forall a. Typeable (NonInj a) => Proxy a -> StaticPtr (NonInj a -> NonInj a) -- f4 Proxy = (static id) :: StaticPtr (NonInj a -> NonInj a) {------------------------------------------------------------------------------- Test 2: adding some kind of universe -------------------------------------------------------------------------------} data U :: * -> * where UB :: U Bool UC :: U Char f5 :: U a -> NonInj a -> NonInj a f5 _ = id -- This works just fine f6 :: (Typeable a, Typeable (NonInj a)) => StaticPtr (U a -> NonInj a -> NonInj a) f6 = static f5 -- but if we introduce Typeable .. f7 :: Typeable a => U a -> NonInj a -> NonInj a f7 _ = id -- .. fakeStatic still works f8 :: (Typeable a, Typeable (NonInj a)) => StaticPtr (U a -> NonInj a -> NonInj a) f8 = fakeStatic f7 -- .. but static leads to a weird error: -- No instance for (Typeable a) arising from a use of ‘f7’ -- f9 :: (Typeable a, Typeable (NonInj a)) => StaticPtr (U a -> NonInj a -> NonInj a) -- f9 = static f7 {------------------------------------------------------------------------------- Test 3: GADT wrapping StaticPtr -------------------------------------------------------------------------------} data Static :: * -> * where StaticPtr :: StaticPtr a -> Static a StaticApp :: Static (a -> b) -> Static a -> Static b -- Serializable types can be embedded into Static; here we just support U StaticBase :: U a -> Static (U a) -- this is fine f10 :: forall a. (Typeable a, Typeable (NonInj a)) => U a -> Static (NonInj a -> NonInj a) f10 x = StaticPtr (fakeStatic f5) `StaticApp` (StaticBase x) -- but this fails with -- Couldn't match type ‘NonInj a -> NonInj a’ -- with ‘NonInj a0 -> NonInj a0’ -- Expected type: U a -> NonInj a -> NonInj a -- Actual type: U a0 -> NonInj a0 -> NonInj a0 -- f11 :: forall a. (Typeable a, Typeable (NonInj a)) => U a -> Static (NonInj a -> NonInj a) -- f11 x = StaticPtr (static f5) `StaticApp` (StaticBase x) -- although in this case we can work around it with a type annotation: -- (note that for f4 above this workaround didn't work) f12 :: forall a. (Typeable a, Typeable (NonInj a)) => U a -> Static (NonInj a -> NonInj a) f12 x = StaticPtr (static f5 :: StaticPtr (U a -> NonInj a -> NonInj a)) `StaticApp` (StaticBase x) {------------------------------------------------------------------------------- End of tests -------------------------------------------------------------------------------} main :: IO () main = putStrLn "Hi" }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13306> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13765: GHC cannot parse valid Haskell98 whose first identifier is named signature
by GHC 28 May '17

28 May '17

#13765: GHC cannot parse valid Haskell98 whose first identifier is named signature -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.2.1-rc2 (Parser) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This no longer parses in GHC 8.2: {{{ ezyang@sabre:~$ cat A.hs signature = 2 ezyang@sabre:~$ ghc-8.0 -c A.hs A.hs:1:1: error: The IO action ‘main’ is not defined in module ‘Main’ ezyang@sabre:~$ ghc-head -c A.hs A.hs:1:11: error: parse error on input ‘=’ Perhaps you need a 'let' in a 'do' block? e.g. 'let x = 5' instead of 'x = 5' | 1 | signature = }}} The problem is that signature is only a keyword in the module header and not in the rest of the code, which means that there is a shift/reduce conflict when you have a `signature` at the top of the module. This is fairly benign bug as you can only trigger it when you have no imports; nevertheless, we should fix it. One possibility is to have a completely different parser entry when you are parsing an `hsig` file so that `signature` never occurs in a module header when you parse a normal Haskell file. ISTR this was modestly more irritating to implement but perhaps it is still not too bad. (Note that the shift/reduce conflict still exists, but since you'll never declare a signature without a module header it is essentially irrelevant.) I discovered this when mpickering pointed out that adding 'signature' to the module header increased the number of shift reduce conflicts. (https://github.com/haskell-suite/haskell-src- exts/pull/355#issuecomment-304536290). This wasn't the case in GHC's parser but only accidentally: there is already a shift reduce conflict when you have a top-level Haddock doc block! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13765> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13760: Review: Fix test output after 'Some tidying up of type pretty-printing'
by GHC 28 May '17

28 May '17

#13760: Review: Fix test output after 'Some tidying up of type pretty-printing' -------------------------------------+------------------------------------- Reporter: alanz | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The commit https://github.com/ghc/ghc/commit/09d5c993aae208e3d34a9e715297922b6ea42b3f updates the output for T7861.stderr so that the test passes after https://github.com/ghc/ghc/commit/ad14efd539377aaf472ad69449dcaf3e679b0e51 Review that fixing the test is the correct option here. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13760> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13238: Harmonise pretty printing of parens in hsSyn
by GHC 28 May '17

28 May '17

#13238: Harmonise pretty printing of parens in hsSyn -------------------------------------+------------------------------------- Reporter: alanz | Owner: alanz Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Phab:D3043 Removes the insertion of parens in the pretty printer for `HsPar`. This is motivated by making it easier to see if there is a problem with the `ppr` round trip capability introduced in #3384. Due to a lack of time, the has not been done for `ParPat` or `HsParTy`. Complete this work. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13238> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #8440: Get rid of the remaining static flags
by GHC 27 May '17

27 May '17

#8440: Get rid of the remaining static flags -------------------------------------+------------------------------------- Reporter: thoughtpolice | Owner: (none) Type: task | Status: patch Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2839, Wiki Page: | Phab:D3615 -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: new => patch * differential: Phab:D2839 => Phab:D2839, Phab:D3615 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8440#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #8440: Get rid of the remaining static flags
by GHC 27 May '17

27 May '17

#8440: Get rid of the remaining static flags -------------------------------------+------------------------------------- Reporter: thoughtpolice | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D2839 Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * status: closed => new * resolution: fixed => Comment: Oops, it looks like there are still a couple of references to static flags in the flag reference. I've submitted Phab:D3615 for this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8440#comment:11> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13735: RankNTypes don't work with PatternSynonyms
by GHC 27 May '17

27 May '17

#13735: RankNTypes don't work with PatternSynonyms -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple PatternSynonyms | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs data PLambda a = Var a | Int Int | Bool Bool | If (PLambda a) (PLambda a) (PLambda a) | Add (PLambda a) (PLambda a) | Mult (PLambda a) (PLambda a) | Eq (PLambda a) (PLambda a) | Lam (a -> PLambda a) | App (PLambda a) (PLambda a) newtype Lam = L { un :: forall a. PLambda a } }}} {{{#!hs llam :: (forall a. a -> PLambda a) -> Lam llam f = L (Lam f) }}} works fine, but does not with pattern synonyms: {{{ -- $ ghci -ignore-dot-ghci tirr.hs -- GHCi, version 8.2.0.20170507: http://www.haskell.org/ghc/ :? for help -- [1 of 1] Compiling Main ( tirr.hs, interpreted ) -- -- tirr.hs:20:25: error: -- • Couldn't match expected type ‘forall a. a -> PLambda a’ -- with actual type ‘a0 -> PLambda a0’ -- • In the declaration for pattern synonym ‘LLam’ -- • Relevant bindings include -- a :: a0 -> PLambda a0 (bound at tirr.hs:20:25) -- | -- 20 | pattern LLam a = L (Lam a) -- | ^ -- Failed, modules loaded: none. -- Prelude> pattern LLam :: (forall a. a -> PLambda a) -> Lam pattern LLam a = L (Lam a) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13735> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12991: panic when using IrredPreds in a type checker plugin.
by GHC 27 May '17

27 May '17

#12991: panic when using IrredPreds in a type checker plugin. -------------------------------------+------------------------------------- Reporter: owen | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I'm working on a type checker plugin that solves constraints expressed with an empty, closed type family of kind Constraint. These show up in the plugin as wanted IrredPred constraints. Unfortunately, something seems to go sideways sometimes when I give solved or unsolvable IrredPreds back to GHC. I've managed to reproduce the error in a minimal-ish plugin. It doesn't try to solve anything, it just returns all the IrredPred constraints back to GHC in a TcPluginContradiction. When compiling a test case that uses the type family in a constraint, it gives the following output: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-apple-darwin): StgCmmEnv: variable not found $dMonad_a5fm local binds for: $trModule $trModule1_r5qI $trModule2_r5rc }}} If I omit the IrredPreds and return an empty TcPluginContradiction, I get 'Could not deduce...' errors as I would expect. Strangley, the panic also goes away if I give an explicit type signature to main in the test case. I'm attaching an archive with 3 files. Plugin.hs has the plugin itself. Compare.hs has the closed type family. The test case that exercises the panic is in Fails.hs. Running {{{ ghc -shared -dynamic --make Test/*.hs -package ghc-8.0.1 }}} in the unpacked directory should reproduce the panic. Adding -dcore-lint does give some potentially useful information: {{{ [3 of 3] Compiling Test.Fails ( Test/Fails.hs, Test/Fails.o ) irred compare [W] irred_a5qq :: l_a5fo[tau:3] ≽ l'_a5fp[tau:3] (CNonCanonical) irred compare [W] irred_a5qr :: l'_a5fp[tau:3] ≽ l_a5fo[tau:3] (CNonCanonical) <no location info>: warning: In the expression: return @ m_a5fl $dMonad_a5fm @ () $dMonad_a5fm :: Monad m_a5fl[tau:3] [LclId, Str=DmdType] is out of scope <no location info>: warning: In the expression: (irred_a5qq, irred_a5qr) irred_a5qq :: s_a5ql[fuv:2] [LclId, Str=DmdType] is out of scope <no location info>: warning: In the expression: (irred_a5qq, irred_a5qr) Argument value doesn't match argument type: Fun type: (Integer ≽ Integer, Integer ≽ Integer) => (Integer ≽ Integer, Integer ≽ Integer) Arg type: s_a5ql[fuv:2] Arg: irred_a5qq *** Offending Program *** $trModule :: Module [LclIdX, Str=DmdType] $trModule = Module (TrNameS "main"#) (TrNameS "Test.Fails"#) oops :: forall l_a572 l'_a573. (l_a572 === l'_a573) => l_a572 -> l'_a573 -> () [LclIdX, Str=DmdType] oops = \ (@ l_a5eW) (@ l'_a5eX) _ [Occ=Dead] _ [Occ=Dead] _ [Occ=Dead] -> () main :: forall (m_a5fl :: * -> *). m_a5fl () [LclIdX, Str=DmdType] main = \ (@ (m_a5fl :: * -> *)) -> $ @ 'PtrRepLifted @ () @ (m_a5fl ()) (return @ m_a5fl $dMonad_a5fm @ ()) (oops @ Integer @ Integer (irred_a5qq, irred_a5qr) 1 0) *** End of Offense *** <no location info>: error: Compilation had errors }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12991> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12648: Stack overflow when using monad-unlift
by GHC 26 May '17

26 May '17

#12648: Stack overflow when using monad-unlift -------------------------------------+------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I found that with the following simple program I could make runghc/ghci crash with `*** Exception: stack overflow`: {{{ #!/usr/bin/env stack -- stack --resolver lts-7.1 --install-ghc runghc --package monad- unlift-0.2.0 {-# LANGUAGE FlexibleContexts #-} import Control.Monad.Trans.Unlift f :: (MonadBaseUnlift m IO) => m a f = do _ <- askUnliftBase return () }}} I'm not super sure if that's OK. Probably not; even if it does trigger an undecideable case, shouldn't ghc tell me about it instead of just crashing? The `monad-unlift` code used is here: https://github.com/fpco/monad- unlift/blob/adb7869adccc66247cbb1a6175277802e9c098e1/monad- unlift/Control/Monad/Trans/Unlift.hs -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12648> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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